Automatic filling machines have been used for rapidly and accurately transferring liquid medications in pre-measured doses to receptacles such as oral dispensers, nebulizer injectors, vials and hypodermic syringes. In order to maintain sterility of the medications and to prevent cross contamination, these automatic filling machines have used individually packaged sterile disposable liquid dispensing sets which include a syringe which functions as the pumping mechanism and compressible and flexible plastic tubing connecting the syringe, the reservoir for the medication and the receptacle to be filled. The flexible plastic tubing is fabricated from pharmaceutically acceptable materials such as medical grade polyvinylchloride.
In order to maintain sterility and to prevent cross contamination of the medication being pumped, internal valving is not used. Instead, the flexible tubing is sequentially opened and closed in coordination with the movement of the syringe plunger by a lever which engages the exterior of the flexible tubing and squeezes it closed.
In addition to transferring liquid medications, the automatic filling machines can also be used to transfer premeasured amounts of any liquid from a reservoir to a receptacle. The transfers can be made under sterile or non-sterile conditions.
An object of this invention is an improved valving mechanism for a liquid automatic filling machine which may be used with flexible tubing of various dimensions.
Another object is a valving mechanism for an automatic filling machine having manual adjustment means to vary the amount of compression of the flexible tubing to insure proper opening and closing thereof during dispensing operations.
Another object is an adjustment device for the valving mechanism which audibly indicates excess compression of the flexible tubing.
Accordingly, the invention relates to a valving mechanism for an automatic filling machine of a type having a reciprocating pump driven by a crank arm, a pair of compressible, flexible tubes, one of which connects a reservoir to the pump and the other connects the pump to a receptacle, and electrical switching means coordinated with the rotation of the pump crank arm. The valving mechanism includes means to maintain the compressible, flexible tubes in generally parallel spaced relation to each other. A pivotally mounted lever having an end portion positined between the tubes is formed as part of the valving mechanism. This lever reciprocates about its pivotal mounting to move the end portion of the lever into and out of engagement with one compressible, flexible tube and then the other. Means controlled by the electrical switching means are provided for reciprocating the lever. Means for individually adjusting the position of each tube relative to the end of the lever are provided so that the lever can compress and completely close a tube at the end of its reciprocal movement.